A large number of techniques for enabling a vehicle to travel in emergency, where a pneumatic tire is punctured while a vehicle is moving, are proposed because of market demands. In some techniques, a core is inserted into a cavity formed between a pneumatic tire and a rim of a wheel. When the pneumatic tire is punctured, the punctured tire is supported by this core. Thereby, run-flat traveling is enabled (For example, refer to Patent Documents 1 and 2).
The run-flat core is configured of a pair of elastic rings, which are disposed on a rim along the respective bead portions of the pneumatic tire, and a circular shell which stretches between the elastic rings, and which extends in the tire circumferential direction. The run-flat core can be used as it is without adding special modifications to an existing wheel, an existing rim and the like, and thus has an advantage that the run-flat core can be accepted in the market with no confusion.
However, when a run-flat core including a circular shell is inserted into a cavity formed between a pneumatic tire and a rim of a wheel, cavity resonance tends to be increased. For this reason, it has been hoped that cavity resonance resulting from the run-flat core is suppressed, and that advantages of the run-flat core are fully utilized.    Patent Document 1: Japanese patent application Kokai publication No. Hei 10-297226    Patent Document 2: Published Japanese translation of international publication for patent application No. 2001-519279